Normally trunk port are used to interconnect between switch or router. Trunks can carry multiple VLANs traffic go through a single link. By using trunking you can extend your VLANs across you network. There are two type of trunking ISL that’s cisco proprietary & 802.1q is industrial standard.
VLAN Trunking Protocol (VTP) is used to synchronise VLAN between switch. By using VTP you don’t need to configure VLAN everywhere. VLANs will be distributed from VTP server. so it’s reduce the time configure the same VLAN everywhere.
In VTP version 1 and version 2 there are three difference mode in VTP.
- Server mode: The switch in server we can create, edit VLANs and advertise to other VTP client and VTP server. VTP server mode also install VLAN that’s advertise from other
- Client mode: In client mode switch cannot create it’s own VLAN, But it can install VLAN that’s advertise from VTP server. When VTP client receive VLAN advertise from VTP server, it will forward the advertise to other VTP in the same domain.
- Transparent mode: VLANs that’s created in VTP transparent mode is locally significant because it’s not forward VTP message to other switch. It's transparently forward VTP, it not install VLAN from other VTP advertisement.
- Reduce mis-configuration
- Centralize VLAN management, We can add, edit, delete vlan on VTP server then it will distributed to other switch in the same VTP domain
- Reduce time to configure the same VLANs everywhere in the network
But there are some problem when using VTP
- VTP server also act as VTP client, it mean VTP server also install VLAN advertise from other VTP server, or VTP client that's have higher revision number. In case you add new switch with higher configuration revision number, it can overwrite the database. So your hold network will have
- VTP is cisco proprietary so it mean not support with other vender.
- VTP version 1 and version 2 not support extended VLAN
That’s why we rarely see VTP using in production environment.